Recent years, proposals have been made on a pneumatic tire in which a film layer of a thermoplastic resin or a thermoplastic elastomer composition obtained by blending an elastomer with a thermoplastic resin is placed as an air-permeation preventive layer on an inner surface of the tire (see Patent Document 1 and Patent Document 2, for instance).
In a case where a pneumatic tire including such a film layer is required to have a high capability of preventing air permeation as a truck tire, a bus tire and a construction vehicle tire, film layers need to be superposed by winding the film layer in a circumferential direction of the tire multiple times (see Patent Document 3, for instance). This is because, if the capability of preventing air permeation is enhanced through making a single film layer thicker, the rigidity of the thicker film layer becomes too high, and a tire making process accordingly becomes difficult. In other words, the superposition of thin film layers allows each film layer to be kept flexible, and concurrently secures a desired capability of preventing air permeation for a pneumatic tire owing to the superposed film layers.
However, when film layers are superposed on one another by winding a film layer in the circumferential direction of a tire multiple times, an interlayer tacking force (bonding force) between the film layers tends to be uneven at different locations due to, for instance, air remaining between the film layers. In addition, when an external force large enough to displace film layers from each other works on the film layers, what is termed as a stick-slip phenomenon (frictional vibrations involving an alternate series of motions and stops due to an external force and a frictional force) tends to occur because the film layers are high in rigidity. For this reason, when the film layers are superposed by winding a film layer in the circumferential direction of the tire multiple times, it is difficult to expand an uncured tire evenly. Furthermore, in a case where the uncured tire is expanded unevenly due to the superposed film layers, the uneven expansion adversely affects the casing structure including a carcass layer and belt layers, and thus causes a problem of deteriorating the uniformity of the tire.
Patent Document 1: Japanese patent application Kokai publication No. Hei. 8-217923
Patent Document 2: Japanese patent application Kokai publication No. Hei. 11-199713
Patent Document 3: Japanese patent application Kokai publication No. Hei. 9-52502